Medical Genetics - KNUR 221

Medical Genetics - KNUR 221

• Instructor: OTABIL
• Email: [email protected]

Introductory Genetics

• Study of heredity and variation.

What is Genetics?

• Branch of biology studying heredity and variation.
• Hereditary units (genes) are passed from one generation to the next.

Early Ideas About Heredity

• Resemblance between parents and children is a clear sign of biological heredity.
• Sexual reproduction is involved in the passing on of traits in humans and animals.
• It was natural to believe semen carried heredity, proving difficult to know exactly how.

Genetics Theories

• Pangenesis: Inherited structures pass characteristics via small amounts to reproductive glands (gonads). Particles (pangenes/gemmules) from all body parts travel to germ cells (eggs and sperm) and are passed to offspring.
• Proposed by Charles Darwin, supported by Aristotle and others in the 19th century.
• Lamarckism: Organisms acquire traits during their lifetime and pass these traits (e.g., muscles, tattoos, scars) onto their offspring.
• Preformation: Tiny preformed parts already exist in the germ cells (sperm or egg).
• Microscopic observation found an idea of a miniature figure (homunculus), for example, in the sperm cell, as the preformed human being.
• Proposed by Jan Swammerdam and Charles Bonnet.
• Epigenesis: Development begins with a simple structure (zygote) and progressively differentiates into different tissues and organs.
• Proposed by Kasper Wolff and Karl Ernst von Baer in the 18th and 19th centuries.

Germplasm Theory

• Proposed by August Weismann as a major challenge to pangenesis.
• Distinguishes between gametic (germ) cells and somatic (body) cells.
• Genetically significant changes in germ cells (sperms and eggs) are transferred to the next generation.
• Changes in the body cells do not pass to the next generation.

Preformation (Details)

• Explains how a zygote develops into a human being.
• Differentation in the body is achieved from cell proliferation and diversification into different tissues (e.g., arms, legs, liver).
• In the 17th century, observers with microscopes believed a miniature full human form (homunculus) existed within the sperm or egg cell.
• Supported by Jan Swammerdam and Charles Bonnet.

Homunculus

• Little man in the sperm cell
• A fundamental concept from preformationism.
• Human body was preformed inside the spermatozoon (sperm)
• Development was only growth & reproduction.

Epigenesis (Details)

• Sex cells (egg and sperm) are uniform.
• Development is composed of various changes and growth, and differentiation of different tissues in the organism.

Conclusions

• Genetic material (DNA) interacts with the environment.
• Epigenesis more accurately describes development of an organism than preformation.
• An organism is not pre-formed in a zygote.

Recommended Textbooks

• Principles of Genetics (8th ed, 1991) - Gardner, Simmons, & Snustad
• Principles of Genetics (4th ed, 1993) - Tamarin
• Modern Genetics (2nd ed, 1984) - Ayala & Kiger Jr.
• Concepts of Genetics (1983)- Klug & Cummings

Explore the fundamentals of Medical Genetics in this quiz for KNUR 221. Delve into topics such as heredity, variation, and early theories of genetics. Understand key concepts that influence the study of genes and their transmission across generations.